Off Duty Carry

I've heard many times that it is most beneficial for cops to carry either their duty weapon or a compact version of it off duty, because it is the weapon you train with the most etc. I certainly agree with this. However, if the duty weapon is, say, an M&P40, and the off duty weapon is a Glock 23, is that really much of an issue? The weapons have different grip angles, however aside from that they are very similar. No thumb safety, striker fired, etc. If comfortable shooting both, is there any reason to not just carry the 23 as opposed to purchasing an M&P40c? Thanks!

Given that some of us carry an auto as primary and a revolver for backup, it's obviously not a huge issue.

The same platform -- let's say the M&P40 Compact to supplement the full size duty M&P40 -- allows spare magazine interchangeability, which can be a convenience when switching between duty and off duty gun, and is a potential life-saver when the off-duty is carried as a backup gun. Trigger reach and as you note, grip angle, will be exactly the same.

But, as you also note, general operation is pretty much the same between the Glock and M&P platforms, unless the latter has manual safety or magazine disconnector safety.